With the transformation of the global energy structure and the increasing awareness of environmental protection, the transportation demand for liquefied natural gas (LNG), as a clean and efficient energy, is growing day by day. As a special ship designed to transport liquefied natural gas, the safety and reliability of LNG ships are directly related to the stability of energy supply and the effectiveness of environmental protection. In this process, methane sensors play a vital role in the LNG ship gas monitoring system.
The working environment of LNG ships is extremely special, and they need to face risks such as ultra-low temperature, high pressure , and potential flammable gas leakage. As the main component of LNG, the leakage of methane may not only cause fire or explosion, but also pose a threat to the life safety of crew members. Therefore, real-time monitoring and early warning of methane concentration is crucial.
The fixed gas detection system realizes real-time monitoring of methane concentration through methane sensors installed in key areas of the ship. These sensors use highly sensitive detection technology that can respond quickly to changes in methane concentration and transmit data to control and alarm systems in real time. Once the methane concentration exceeds the preset safety threshold, the system will immediately trigger an alarm to remind the crew to take appropriate measures to effectively prevent potential safety risks.
The use of methane sensors in fixed gas detection systems offers several advantages. First, they have high sensitivity and selectivity, allowing them to accurately detect the presence and concentration changes of methane. Secondly, the sensor has the characteristics of rapid response and can complete detection and send out alarm signals in a short time. In addition, the methane sensor has good stability and reliability and can operate stably for a long time in harsh working environments.
In addition to real-time monitoring and early warning functions, methane sensors can also provide valuable information through data analysis. For example, through the analysis of sensor data, the methane leakage of ships during transportation can be understood, providing a basis for subsequent maintenance and repairs. In addition, potential safety risks can be predicted and corresponding preventive measures can be formulated based on the changing trend of methane concentration.
However, the application of methane sensors also faces some challenges. For example, due to the special working environment of LNG ships, sensors need to withstand harsh conditions such as ultra-low temperature and high pressure. In addition, the accuracy and stability of sensors also need to be continuously improved to adapt to more complex monitoring needs.
For real-time monitoring of methane concentration, the Industry and Mining Network recommends catalytic combustion methane sensors and infrared (NDIR) methane sensors:
Catalytic combustion methane sensor :
Japanese Figaro catalytic combustion methane sensor TGS6814, TGS6814 is a catalytic combustion gas sensor, which is TGS6812 upgraded version. It can detect methane gas at the lower explosion limit of 100% LEL level, and can also detect H2. This sensor not only has excellent durability and fast response capabilities, but at the same time, its linear output and high output stability are also its main features. The TGS6814 has a specially designed filter layer inside the cap , making it very low cross-sensitivity to organic vapors. In addition, this sensor has better tolerance to silicon compounds and is more adaptable to harsh environments.
British alphasense catalytic combustion methane sensor (CH4 sensor) – CH-A3, CH-A3 uses the thermal effect principle of catalytic combustion. It consists of a detection element and a compensation element paired to form a measurement bridge. When encountering flammable gas, the flammable gas will When combustion occurs on the surface of the detection element carrier and the catalyst, the temperature of the carrier increases, and the resistance of the platinum wire inside it also increases accordingly, causing the balance bridge to lose balance and output an electrical signal proportional to the concentration of combustible gas.
Infrared (NDIR) methane sensor:
British Clairair infrared gas sensor – S509-CH4,The S509 infrared gas sensor is developed based on Beer-Lambert’s law and infrared spectrum theory, and can accurately detect methane, carbon dioxide, hydrocarbons, etc. It can work in high-humidity environments, has a long service life, has a standard interface output, and has simple peripheral circuits .
Dynament Hydrocarbon Sensor – MSH-PS/HC: The Dynament Hydrocarbon Sensor MSH-PS/HC can measure methane gas in the range of 0-100% and propane gas in the range of 0-2%. The sensor uses non-dispersive infrared technology and can respond to hydrocarbon gases, including methane and propane.
British Alphasense infrared methane sensor thermopile detector – IRM-AT, IRM-AT is a small-size infrared CH4 gas sensor that uses non-dispersive infrared (NDIR) technology to detect gases. Different gases detect infrared at different concentrations. The absorption rate of the spectrum is different to detect the presence and concentration of the target gas and is not easily affected by the harsh environment on site. It adopts dual-channel sampling technology, which can self-suppress zero point drift. It has the characteristics of long calibration cycle, strong anti-interference ability, high precision, high reliability and long service life.
British Clairair high-resolution infrared methane sensor (NDIR CH4 sensor) Prime1 , Prime1 sensor uses NDIR technology to detect gas concentration. There is an infrared light source inside the sensor, a dual-element infrared detector, a unique optical waveguide to allow the gas to diffuse in, an ARM7 core microprocessor, and the output voltage provided by the circuit is independent of the power supply polarity. The sensor can be set to a linear voltage output, with a full-scale range of 0.4V-2.0V, referenced to the negative pole of the power supply, or to a catalytic combustion format output. Usually the zero point is the intermediate voltage, which is 100mV relative to the voltage of the detection pin at the full-scale point. In addition, the serial connection allows reading of output values and access to internal configuration. The communication connection points are pads on the Prime1 of the 3 series and pins on the Prime1 of the 5 series. The internal integrated circuit can realize functions such as driving optical devices, extracting detection signals, converting signal intensity into concentration, performing temperature compensation and quantifying output values, etc. In catalytic combustion configuration, Prime1 can completely replace the catalytic combustion sensor without changing the circuit without changing the power supply requirements. When Prime 1 is used in a constant current catalytic combustion circuit, the peripheral components need to meet the power supply requirements. Prime1 currently does not have explosion-proof certification, so if it is used in hazardous areas, it must be equipped with an explosion-proof sealed enclosure. 0.01% high resolution, measuring range is 0-10%Vol; 0.1% resolution, measuring range is 10-100%Vol.
British GSS NDIR CH4 sensor FlameIR-ME1
FlameIR®-ME1 is an ultra-low power NDIR CH4 sensor using advanced solid-state LED optical technology.
FlameIR®-ME1 is calibrated for concentrations up to 0-5% methane (100% LEL).
FlameIR®-ME1 consumes an average of ~3.6mW (at lower when sampling period is shortened), making it compatible with mains-powered or wearable applications
The FlameIR®-ME1 typically has a reading accuracy better than 0.01% + 3% of the sensor’s full scale
The FlameIR®-ME1 has built-in zero tracking for Maintaining CH4 measurement accuracy over the life of the product
FlameIR®-ME1 will be intrinsically safe certified to ATEX II GD Ex ia IIC T4 Gb.
In general, methane sensors play an irreplaceable role in the LNG ship gas monitoring system. With the continuous advancement of technology and the continuous expansion of application scenarios, the performance of methane sensors will continue to improve, providing more reliable technical support for the safe transportation of LNG ships. At the same time, we should also pay attention to the innovation and development of sensor technology to meet the future needs of the LNG transportation industry for higher safety and reliability.
